A Professor Morris Puzzle is more than the problem you see. Solving the problem is the starting point for further discussion and investigation. Notes are provided to support that process.
Multiplication, commutative law
Task Centre Connection
Task 17: Truth Tiles 2
Task 19: Cookie Count
Task 30: Truth Tiles
Task 123: Bob's Buttons
Make a model, write an equation
Puzzle 9 has a similar problem involving five hands, each with four fingers. Clearly the answer to each puzzle is 20. Also the pair of puzzles shows that 4 x 5 = 5 x 4. But more importantly the puzzles demonstrate the importance of context, for in these cases 4 x 5 does not mean the same as 5 x 4.